<template> 
    <div>
      <el-upload action="http://edu-xing.oss-cn-hangzhou.aliyuncs.com" :data="dataObj" list-type="picture"
        :multiple="false" :show-file-list="showFileList" :file-list="fileList" :before-upload="beforeUpload"
        :on-remove="handleRemove" :on-success="handleUploadSuccess" :on-preview="handlePreview">
        <el-button size="small" type="primary">点击上传</el-button>
        <div slot="tip" class="el-upload__tip">只能上传jpg/png文件，且不超过10MB</div>
      </el-upload>
      <el-dialog :visible.sync="dialogVisible">
        <img width="100%" :src="fileList[0].url" alt="">
      </el-dialog>
    </div>
  </template>
  <script>
  import { policy } from './policy'
  import { getUUID } from '@/utils'
  
  export default {
    name: 'singleUpload',
    props: {
      value: String
    },
    computed: {
      imageUrl() {
        return this.value;
      },
      imageName() {
        if (this.value != null && this.value !== '') {
          return this.value.substr(this.value.lastIndexOf("/") + 1);
        } else {
          return null;
        }
      },
      fileList() {
        return [{
          name: this.imageName,
          url: this.imageUrl
        }]
      },
      showFileList: {
        get: function () {
          return this.value !== null && this.value !== '' && this.value !== undefined;
        },
        set: function (newValue) {
        }
      }
    },
    data() {
      return {
        dataObj: {
          policy: '',
          signature: '',
          key: '',
          ossaccessKeyId: '',
          dir: '',
          host: '',
          // callback:'',
        },
        dialogVisible: false
      };
    },
    methods: {
      emitInput(val) {
        this.$emit('input', val)
      },
      handleRemove(file, fileList) {
        this.emitInput('');
      },
      handlePreview(file) {
        this.dialogVisible = true;
      },
      beforeUpload(file) {
        let _self = this;
        return new Promise((resolve, reject) => {
          policy().then(response => {

            //意思是说policy获取签名后，把签名信息保存起来
            _self.dataObj.policy = response.data.policy;
            _self.dataObj.signature = response.data.signature;
            _self.dataObj.ossaccessKeyId = response.data.accessid;
            _self.dataObj.key = response.data.dir + getUUID() + '_${filename}';
            _self.dataObj.dir = response.data.dir;
            _self.dataObj.host = response.data.host;
            resolve(true)

            //总的来说是什么意思啊？
            //上传之前先请求签名，保存起来签名
            //根据action="http://edu-xing.oss-cn-hangzhou.aliyuncs.com"
            //结合data信息，提交到云端
          }).catch(err => {
            reject(false)
          })
        })
      },
      handleUploadSuccess(res, file) {
        console.log("上传成功！ flie:",file);
        this.showFileList = true;
        this.fileList.pop();
        this.fileList.push({ name: file.name, url: this.dataObj.host + '/' + this.dataObj.key.replace("${filename}", file.name) });
        this.emitInput(this.fileList[0].url);
      }
    }
  }
  </script>
  <style>
  </style>
  
  
  